A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

A laser apparatus includes a light source unit and a light combining unit. The light source unit outputs first laser light and second laser light having a wavelength different from that of the first laser light to different optical paths. The light combining unit is optically coupled to the light source unit, and combines the first laser light and the second laser light to generate a burst pulse with a frequency according to a difference between the wavelength of the first laser light and the wavelength of the second laser light. In the light source unit, the wavelengths of the first laser light and the second laser light are set in advance or settable such that the frequency of the burst pulse is 1 GHz or more.

The present application provides a terahertz spectrum measurement system and a method for analyzing a terahertz spectrum of a substance, wherein the terahertz spectrum measurement system comprises: two terahertz quantum cascade lasers with their emission ports arranged oppositely; and a vacuum hood arranged between the emission ports of two terahertz quantum cascade lasers. The terahertz spectrum measurement system and the method for analyzing a terahertz spectrum of a substance realize a separate terahertz dual frequency comb while retaining the advantages of the on-chip dual frequency comb system, which solves the problem that the on-chip dual frequency comb cannot directly measure the terahertz spectra of substances.

Methods and apparatus to control the optical frequency of a laser are disclosed. An apparatus includes: a first laser to emit a first beam of light, the first beam of light to have an adjustable frequency based on an input current; a second laser to emit a second beam of light, the second beam of light to have a substantially fixed frequency; a photodetector to generate a feedback signal indicative of a frequency difference between the first and second beams of light; and logic circuitry to control the input current based on the feedback signal.

A method for physical random number generation includes the steps of: modulating the gain of a vertical-cavity surface-emitting laser periodically from the lower threshold to the upper threshold and back; maintaining the gain per round trip positive for a longer period than the round trip time of the cavity; maintaining the net gain per round trip negative for a longer period than the round trip time of the cavity, in order to create optical pulses of random amplitude; detecting the optical pulses; converting the optical pulses into electrical analog pulses; and digitising the electrical analog pulses into random numbers.

Low phase noise signal generated in a small structure is required for communication and high-resolution imaging. A DBR based multi-mode laser is combined with mode-locking method to build frequency stabilized and tunable RF signal generator. The number of the output modes from each laser is adjusted using reflecting bandwidth of distributed Bragg reflector and electro-absorption (EA) modulator for amplitude control, while the phase section in integrated laser system provides frequency tuning. Mode-locking of 60 laser modes results in a highly frequency stable 10 GHz RF beat-notes with a calculated phase noise of −150 dBc/Hz at 10 kHz offset frequency.

A method and system for using a wavelength tunable semiconductor laser as an excitation source of a fiber optics sensing system (FOSS) based on a thermoelectric control of a laser sweep. A device can include an optical fiber; a set of fiber Bragg gratings disposed within the optical fiber; a single-frequency laser (SFL) operatively connected to the optical fiber; a thermoelectric cooler operatively connected to the SFL; a controller comprising a processor in communication with the thermoelectric cooler; and a nontransitory, computer-readable storage medium in communication with the processor. The nontransitory, computer-readable storage medium can store instructions that, when executed by the processor, cause the processor to perform operations including determining a strain value at a first fiber Bragg grating of the set of fiber Bragg gratings based on a second laser signal received at the device that is reflected from an interaction of a first laser signal with the first fiber Bragg grating.

A laser apparatus includes: a light source configured to generate laser light; and an optical negative feedback unit configured to narrow a spectral line of the laser light using optical negative feedback. A modulation signal is input to the light source to modulate a frequency of the laser light. A modulation amount in the frequency of the laser light is detected. A modulation sensitivity is calculated from (i) the modulation amount and (ii) an intensity of the modulation signal.